The invention relates to a method for the insertion of a weft thread in a rapier weaving machine in accordance with the preamble of claim 1, to a system for carrying out the method and to a rapier weaving machine with a system of this kind.
An inserting rapier and a receiving rapier are used in rapier weaving machines for the insertion of the weft thread, with the weft thread transfer taking place approximately in the middle of the web width.
Each rapier is provided with a thread clamp.
In principle two kinds of thread clamps are used.
1. Positively "controlled thread clamps", with the thread receiving and releasing taking place via the corresponding thread clamp through closing and opening by means of an actuation means.
2. Negative or "automatically clamping thread clamps", with the thread receiving and releasing taking place through drawing of the thread into or out of the previously set clamping region respectively.
In a rapier weaving machine with a transfer of the weft thread in the middle of the fabric width the inserting rapier and the receiving rapier can each be equipped with similar thread clamps or with different thread clamps, i.e. negative, positive or a mixed form of clamp types.
If weft yarns of highly differing thickness or unequal smoothness are used for the manufacture of a certain cloth, an average clamping force or width of the clamping gap respectively is determined by experiments and the thread clamp is firmly set correspondingly. With the thus set thread clamp both a thick and a thin weft thread are inserted. The setting of the thread clamp is carried out predominantly in accordance with the thinner yarn in order that the latter does not slip out of the clamp during the weft insertion. A thicker yarn is accordingly mostly either squashed excessively or only insufficiently clamped with the same setting of the thread clamp and with substantially the same contour of the clamping body. The negative thread clamps have, in particular, the disadvantages that thread residues or fibrils respectively remain in the thread clamp of the inserting rapier when the weft thread is taken over by the receiving rapier, or that e.g. the thicker weft thread is already lost prior to it being taken over by the rapiers.